Molybdenum based oxidation catalysts

ABSTRACT

This invention concerns catalysts comprising a molybdenum compound of formula (I): V q MoA y O z , (II): NiMo x B y O z ′, (III): VNi w Mo x C y ′O z ″, (IV): CoNi w Mo x D y O z ′″, or (V): VNi w CO r Mo x E y O z ″″, wherein: A is at least one cation selected from the group consisting of cations of Cr, Sb, Co, Ce and Pb; B is at least one cation selected from the group consisting of cations of Sb, Al and W; C is at least one cation selected from the group consisting of cations of Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn; D is at least one cation selected from the group consisting of cations of Ba, Mn, Al, Sb, Sn and W; E is at least one cation selected from the group consisting of cations of Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb; q, r, w, x, y, y′, z, z′, z″, z′″ and z″″ are as defined in the disclosure. These catalysts can be used in C4 oxidation processes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US97/16563, filed Sep. 18, 1997 which claims priority benefit fromProvisional Application No. 60/026,597, filed Sep. 24, 1996.

FIELD OF THE INVENTION

This invention relates to compounds comprising molybdenum, oxygen andcertain cations, and the use of these compounds as catalysts in C₄oxidation processes, especially butane oxidation processes.

TECHNICAL BACKGROUND

Oxidative organic processes are widely used in industrial operations.One commercially valuable process involves the oxidation of butane tomaleic anhydride. Maleic anhydride is used as a raw material forproducts ranging from agricultural chemicals, paints, paper sizing andfood additives to synthetic resins. To fill the high demand for thisvaluable chemical, a variety of commercial processes have beendeveloped.

One important route to maleic anhydride involves the vapor phaseoxidation of n-butane over a vanadium/phosphorus oxide (VPO) catalyst.The reaction step involves oxidation of n-butane with air (oxygen) toform maleic anhydride, carbon oxides, water and smaller amounts ofpartially oxidized by-products. Typically, the process is carried out infixed-bed reactors, fluid-bed reactors, or more recently inrecirculating solids reactors having two reaction zones in which twoseparate reactions take place with a catalyst (the solid) circulatingbetween the two reaction zones and taking part in reactions in bothzones.

A number of non-VPO catalysts have been reported in the literature.Zazhigalov, V. A. et al., in an article entitled “Oxidation of n-butaneon Vanadium Molybdenum-Oxide Catalysts”, Inst. Fiz. Khim. im.Pisarzhevskogo, Kiev USSR Neftekhimiya (1977), 17 (2), 268-73 describethe activity of V₂O₅-MoO₃ catalysts in butane oxidation as passingthrough a maximum at 25% MoO₃, and that a certain catalytic structureconsisting of, V⁴⁺, V⁵⁺ and Mo⁶⁺ ions correspond to their preferredcatalyst composition. These results obtained at 500-600° C. indicate lowcatalyst activity at normal operating temperatures.

Mazzochia, C. R. et al., in “Selective Oxidation of Butane in thePresence of NiO—MoO₃ catalysts”; An. Quim. Ser. A 79, no. 1108-113(1983) disclose nickel molybdate catalysts prepared bycoprecipitation that exhibit low hydrocarbon conversions. At 475° C.,19% conversion of n-butane was noted with low selectivities to maleicanhydride.

Umit Ozkan and G. L. Schrader, in “Synthesis, Characterization andcatalytic behaviour of cobalt molybdates for 1-butene oxidation tomaleic anhydride”, Applied Catalysis, 23 (1986) 327-338 disclose the useof cobalt molybdate for the oxidation of 1-butene.

In spite of the progress in catalyst and process development over theyears, a need still remains for improved non-VPO catalysts useful in theoxidation of C4 hydrocarbons, particularly n-butane, to maleic anhydrideand especially catalysts which are active at lower temperatures and haveshorter contact times; and it is to that end that the present inventionis directed.

SUMMARY OF THE INVENTION

The present invention provides a catalyst. comprising a molybdenumcompound of formula I, II, III, IV or V:

V_(q)MoA_(y)O_(z)  I

NiMo_(x)B_(y)O_(z)′  II

VNi_(w)Mo_(x)C_(y)′O_(z)″  III

CoNi_(w)Mo_(x)D_(y)O_(z)′″  IV

VNi_(w)Co_(r)Mo_(x)E_(y)O_(z)″″  V

wherein:

q is a number from 0.1 to 10;

r is a number from 0.1 to 10;

w is a number from 0.1 to 10;

x is a number from 0.1 to 10;

y is a number from 0.1 to 10;

y is a number from 0 to 10,

A is at least one cation selected from the group consisting of cationsof: Cr, Sb, Co, Ce and Pb;

B is at least one cation selected from the group consisting of cationsof: Sb, Al and W;

C is at least one cation selected from the group consisting of cationsof: Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn;

D is at least one cation selected from the group consisting of cationsof: Ba, Mn, Al, Sb, Sn, and W;

E is at least one cation selected from the group consisting of cationsof: Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb; and

z, z′, z″, z′″, and z″″ are determined using the amounts and oxidationstates of all cations present in each formula according to the followingequations:

z=((q times oxidation state of V)+(1 times oxidation state of Mo)+(ytimes oxidation state of A)) divided by 2 (oxidation state of oxygen);

z′=((1 times oxidation state of Ni)+(x times oxidation state of Mo)+(ytimes oxidation state of B)) divided by 2 (oxidation state of oxygen);

z″=((1 times oxidation state of V)+(w times the oxidation state ofNi)+(x times oxidation state of Mo)+(y′ times oxidation state of C))divided by 2 (oxidation state of oxygen);

z′″=((1 times oxidation state of Co)+(w times the oxidation state ofNi)+(x times oxidation state of Mo)+(y′ times oxidation state of D))divided by 2 (oxidation state of oxygen); and

z″″=((1 times oxidation state of V)+(w times the oxidation state ofNi)+(r times the oxidation state of Co)+(x times oxidation state ofMo)+(y times oxidation state of E)) divided by 2 (oxidation state ofoxygen).

The present invention also provides a process for the oxidation of a C4hydrocarbon to maleic anhydride, comprising: contacting the C4hydrocarbon with a source of oxygen in the presence of a catalyticamount of a molybdenum catalyst comprising a compound of formula I, II,III or V, as defined above, to yield maleic anhydride.

The present invention further provides a process for the oxidation ofn-butane to maleic anhydride, comprising contacting n-butane with asource of oxygen in the presence of a catalytic amount of a molybdenumcatalyst comprising a compound of formula IV, as defined above, whereinthe molybdenum catalyst is in a bulk state, to yield maleic anhydride.

The present invention also provides a process for the oxidation ofn-butane to maleic anhydride, comprising: contacting n-butane with asource of oxygen in the presence of a catalytic amount of a catalystcomprising a molybdenum compound of formula VI or VII in a crystalline,active phase

V₉Mo₆O₄₀  VI

V₂MoO₈  VII

to yield maleic anhydride.

The present invention also provides a process for the preparation of amolybdenum compound comprising a crystalline oxide of formula I, II,IlI, IV or V, as described above, comprising the steps of: contacting atleast one compound having a cation of the molybdenum compound with atleast one cation containing compound for each of the other cations ofthe molybdenum compound in a solution comprising water to form aresultant solution or colloid; freezing the resultant solution orcolloid to form a frozen material, freeze drying the frozen material;and heating the dried frozen material to yield the molybdenum compoundof formula I, II, III, IV, V, VI or VII.

DETAILED DESCRIPTION OF THE INVENTION

Multicomponent catalyst systems have been identified herein wherein thepresence of molybdenum in combination with other particular cations showa significant beneficial effect on catalyst performances compared withmany non-VPO catalysts reported in the literature for n-butaneoxidation. These new multicomponent catalysts of the present inventioncomprise a molybdenum compound of formula I, II, III, IV or V:

V_(q)MoA_(y)O_(z)  I

NiMo_(x)B_(y)O_(z)′  II

VNi_(w)Mo_(x)C_(y)′O_(z)″  III

CoNi_(w)Mo_(x)D_(y)O_(z)′″  IV

VNi_(w)Co_(r)Mo_(x)E_(y)O_(z)″″  V

wherein: q is a number from 0.1 to 10; r is a number from 0.1 to 10; wis a number from 0.1 to 10; x is a number from 0.1 to 10; y is a numberfrom 0.1 to 10; and y′ is a number from 0 to 10.

A is at least one cation selected from the group consisting of cationsof: Cr, Sb, Co, Ce and Pb. A is preferably Sb, and a preferred compoundof formula I is V₁Mo₁Sb₁O_(z). B is at least one cation selected fromthe group consisting of cations of: Sb, Al and W. B is preferably Sb,and a preferred compound of formula II is Ni₁Mo_(2.3)Sb₁O_(z)′. C is atleast one cation selected from the group consisting of cations of: Fe,Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn. C is preferably Bi, or Nb and Sn,and preferred compounds of formula III are V₁Mo_(2.3)Ni₁Bi₁O_(z)″ andV₁Mo_(2.3)Ni₁Nb₁Sn₁O_(z)″. D is at least one cation selected from thegroup consisting of cations of: Ba, Mn, Mo, Al, Sb, Sn, and W. D ispreferably Sn or W, and preferred compounds of formula IV areCo_(0.5)Ni_(0.5)Mo₃Sn_(0.5)O_(z)′″ and Mo₃Co_(0.5)Ni_(0.5)W₁O_(z)′″. Eis at least one cation selected from the group consisting of cations of:Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb. E is preferably Fe, Sr, Zr,Ga or Pb, and preferred compounds of formula V areV₁Mo_(2.3)Ni_(0.5)Co_(0.5)Fe₁O_(z)″″,V₁Mo_(2.3)Co_(0.5)Ni_(0.5)Sr₁O_(z)″″.V₁Mo_(2.3)Co_(0.5)Ni_(0.5)Zr₁O_(z)″″,V₁Mo_(2.3)Co_(0.5)Ni_(0.5)Ga₁O_(z)″″ andV_(l)Mo_(2.3)Co_(0.5)Ni_(0.5)Pb_(l)O_(z)″″.

The ranges for z, z′, z″, z′″, and z″″ defining the subscript for oxygenin the formulae I-V, varies widely. The value of z, z′, z″, z′″, and z″″is defined using the range of possible oxidation states of all of thecations found in the molybdenum compound as shown below.

For the molybdenum compounds of formula I, the highest oxidation statesof the A cations are: V⁵⁺, Mo⁶⁺, Cr⁶⁺, Sb⁵⁺, Co³⁺, Ce⁴⁺ and Pb⁴⁺; andthe lowest oxidation states for the A cations are: V³⁺, Mo⁴⁺, Cr²⁺,Sb³⁺, Co²⁺, Ce³⁺ and Pb²⁺. Therefore, for example, when the molybdenumcompound of formula I is V₁₀Mo₁A₁₀O_(z), wherein A is Cr, the maximumvalue for z. z_(max), is: z_(max)=((10×5)+(1×6)+(10×6))÷by 2=116/2=58.The minimum value for z, z_(min), in formula I wherein A is Cr is:z_(min)=((10×3)+(1×4)+(10×2))÷by 2=54/2=27. When the molybdenum compoundof formula I is V_(0.1)Mo₁A_(0.1)O_(z), wherein A is Pb,z_(max)=((0.1×5)+(1×6)+(0.1×4))÷by 2=6.9/2=3.45. The minimum value forz, z_(min), in formula I wherein A is Pb is:z_(min)=((0.1×3)+(1×4)+(0.1×2))÷by 2=4.5/2=2.25. Thus, for molybdenumcompounds of formula I, z ranges from 2.25 to 58.

For molybdenum compounds of formula II, the highest oxidation statesare: Ni³⁺, Mo⁶⁺, Sb⁵⁺, Al³⁺, and W⁶⁺ and the lowest oxidation statesare: Ni²⁺, Mo²⁺, Sb³⁺, Al³⁺, and W²⁺. z′_(max) and z′_(min) can becalculated as shown above for z_(max) and z_(min) of formula I.

For molybdenum compounds of formula III, the highest oxidation statesare: V⁵⁺, Ni³⁺, Mo⁶⁺, Fe³⁺, Zn²⁺, Al³⁺, Sb⁵⁺, Bi⁵⁺, W⁶⁺, Li¹⁺, Ba²⁺,Nb⁵⁺, and Sn⁴⁺, and the lowest oxidation states are: V²⁺, Ni²⁺,Mo^(2+, Fe) ²⁺, Zn²⁺, Al³⁺, Sb³⁺, Bi³⁺, W²⁺, Li¹⁺, Ba²⁺, Nb³⁺, and Sn²⁺.z″_(max) and z″_(min) can be calculated as shown above for z_(max) andz_(min) of formula I. Since there can be mixtures of the C cations,these must be factored into the ranges for z.

For molybdenum compounds of formula IV, the highest oxidation statesare: Co³⁺, Ni³⁺, Mo⁶⁺, Ba²⁺, Mn⁷⁺, Al³⁺, Sb⁵⁺, Sn⁴⁺, and W⁶⁺, and thelowest oxidation states are: Co²⁺, Ni²⁺, Mo²⁺, Ba²⁺, Mn²⁺, Al³⁺, Sb³⁺,Sn²⁺, and W²⁺. z′″_(max) and z′″_(min) can be calculated as shown abovefor z_(max) and z_(min) of formula I.

For molydbenum compounds of formula V, the highest oxidation states are:V⁵⁺, Ni³⁺, Co³⁺, Mo⁶⁺, Fe³⁺, Ca²⁺, Mn⁷⁺, Sr²⁺, Eu³⁺, La³⁺, Zr⁴⁺, Ga³⁺,Sn⁴⁺ and Pb⁴⁺, and the lowest oxidation states are: V²⁺, Ni²⁺, Co²⁺,Mo²⁺, Fe²⁺, Ca²⁺, Mn²⁺, Sr²⁺, Eu²⁺, La³⁺, Zr⁴⁺, Ga³⁺, Sn²⁺ and Pb²⁺.z″″_(max) and z″″_(min) can be calculated as shown above for z_(max) andz_(min) of formula I.

The catalysts of the present invention can be either a particularstructure (containing a certain ratio of cations) or a combination ofstructures and thus comprise a mixture of the crystalline oxides of themolybdenum compound of formula I, II, III, IV or V and may furthercomprise the amorphous phase of the compound.

The molybdenum compounds of the present invention can be prepared byvarious methods, for example, by freeze drying, alcohol reflux and geltechniques. Spray roasting, spray drying and coprecipitation could alsobe employed. Ceramic methods, i.e., solid state techniques could be usedbut are, in general, less preferred. Certain compounds of formulas I-Vare better prepared by one method over another as appreciated by one ofordinary skill in the art.

The catalyst preparative process is usually conducted at normalatmospheric pressure, but elevated or reduced pressures can be employed.Agitation is not required, but is usually provided to facilitate ahomogeneous mix and to facilitate heat transfer.

One process for the preparation of a catalyst comprising a molybdenumcompound of formulas I, II, III, IV, V, VI or VII, as described above,comprises contacting at least one cation containing compound with atleast one cation containing compound for each of the other cations ofthe final molybdenum compound in a solution comprising water to form aresultant solution or colloid; freezing the resultant solution orcolloid to form a frozen material; freeze drying the frozen material;and heating the dried frozen material to yield the molybdenum compoundof formula I, II, III, IV, V, VI or VII.

The compound containing a cation of the final molybdenum compound offormula I, II, III, IV, V, VI or VII can be a salt, oxide or the like.The cation containing compounds are contacted with each other upon theiraddition to the solution comprising water. There is at least one cationcontaining compound for each of the cations in the molybdenum compoundof formula I, II, III, IV, V, VI or VII. Each cation can be contained ina separate cation containing compound or more than one cation can becontained in the same cation containing compound. There can also be morethan one cation containing compound for each cation in the finalmolybdenum compound of formulas I, II, III, IV. V, VI or VII. The cationcontaining compounds can be ammonium or sodium salts of molybdic acid,vanadic acid or tungstic acid, in addition to compounds containing theA, B, C, D, E cation of choice or other cations present in the finalmolybdenum compound of formulas I, II, III, IV, V, VI or VII. Forexample, the oxides or acetylacetonates, chlorides or acetates of Li,Cr, Mn, Mo, Fe, Co, Ni, Ce, W, Zn, Sr, Nb, Eu, Ba. Zr, Al, Ca, Sn, Pb,Sb, Bi, La and Ga can be cation containing compounds. Representativeexamples of such salts or oxides containing cations of the finalmolybdenum compound of formula I, II, III, IV, V, VI or VII can be foundin Tables 1-6 of the present invention. Normal commercially availablereagents can be used for the cation containing compounds used in thepreparation of the molybdenum compound. The highest purity productsattainable need not be employed: however the purity of the reagents mustbe known in order to calculate the gross amount required. In additionthe reagents should not be contaminated with any catalyst poison. Theamount of reagent employed should be within plus or minus 5%, preferablywithin plus or minus 2% of the amount indicated by stoichiometry.

The cation containing compounds are dissolved in an appropriate solventto form a solution or fine colloid. The formation of a solution, asopposed to a colloid, is generally preferred for most effective mixing.

In cases where NH₄VO₃ is the cation containing compound used, NH₄VO₃salt can be dissolved in water prior to adding the other cationcontaining compounds by heating water or other appropriate solvents. Theadditional cation containing compounds can then be added to form aresultant solution or a finely mixed colloid. The resultant solution orcolloid is rapidly frozen at liquid nitrogen temperatures. Rapidfreezing ensures the cation containing compounds will remain intimatelymixed and will not segregate to any significant degree. The frozenmaterial can then be transferred to a freeze drier, such as a VirtisFreeze Drier (Baltimore, Maryland) equipped with a Unitop unit. Thesolution is kept frozen while water vapor is removed by evacuation. Inorder to prevent melting of the frozen material. the freeze drier can bemaintained at a temperature ranging from about 0° C. to about −40° C.,preferably between −40° C. to −20° C. with a vacuum of 2-10 millitorr.After at least 24 hours, preferably about 2-4 days, the dried sample canbe calcined (heated) in air at a temperature ranging from about 250° C.to about 500° C., preferably about 400° C. for a time sufficient todecompose the cation containing compounds of formula I, II, III, IV, V,VI or VII to form metal oxide phases. This will require heating for aperiod of about 0.5 hours to about 24 hours.

Freeze drying methods can produce mixtures of solid cation containingcompounds which are nearly as well mixed as their solution counterparts.The method is superior to slower solvent evaporation because homogeneitycan be lost during the removal of solvent. In addition. in many casesbecause the cation containing compounds are well mixed, a lowercalcination temperature can be used, and can allow for the synthesis ofmetal oxides with higher surface areas than typically observed bytraditional high temperature ceramic syntheses. Choice of calcinationtemperature and protocols and atmosphere can also influence the types ofphases synthesized.

Another process for the preparation of a catalyst comprising amolybdenum compound of formula I, II, III, IV, V, VI or VII, asdescribed above, comprises the steps of: mixing a solution comprising atleast one cation containing compound for each of the cations in themolybdenum compound of formula I, II, III, IV, V, VI, VI or VII and analcohol to form a suspension; heating the suspension to reflux; andisolating the molybdenum compound of formula I, II, III, IV, V, VI orVII.

At least one cation containing compound for each of the cations in themolybdenum compound of formula I, II, III, IV, V, VI or VII are combinedwith an alcohol or combination of alcohols, such as ethyl alcohol, ethylalcohol/benzyl alcohol mixtures, 1-propanol, 1-butanol, isobutylalcohol, 2-methyl-2 propanol, 1-heptanol, neopentyl alcohol, phenol orthe like, to form a suspension. The cation containing compounds can bethose as described above for the freeze drying process. Mixing oragitation can be supplied via methods known in the art. The preparationcan be carried out in a dry box to prevent any hydration. The resultingsuspension is next heated to reflux under an inert atmosphere, such asnitrogen, for a time sufficient to ensure a proper solution. After thesolution is formed, the solvent can be removed by freeze drying,rotary-evaporation, or a slow drying process after filtering, decantingor the like. The dried material can then be calcined at a temperatureranging from about 250° C. to about 500° C., preferably about 400° C.,under air for a time sufficient to form the molybdenum compound offormula I, II, III, IV, V, VI or VII. This can take from about 0.5 hoursto about 24 hours.

A further process for the preparation of a catalyst comprising amolybdenum compound of formula I, II, III, IV, V, VI or VII, asdescribed above. comprises the steps of: contacting at least one cationcontaining compound for each cation of the molybdenum compound offormula I, II, III, IV, V, VI or VII with at least one cation containingcompound for each of the other cations in the molybdenum compound offormula I, II, III, IV, V, VI or VII in a solution comprising water toform a resultant solution or colloid; stirring the resultant solution orcolloid until gelation occurs; and drying the gel to yield themolybdenum compound of formula I, II, III, IV, V, VI or VII.

The cation containing compounds for this gel process can be those asdescribed above for the freeze drying process. Following contact of thecation containing compounds with each other, the resultant solution orcolloid is stirred until gelation occurs. In some cases an adjustment ofpH is needed to induce gelation. Acid or base can be added depending onthe nature of the other ingredients being used in the preparation of themolybdenum compound. Gelation can occur at room temperature atatmospheric pressure. The resulting gel can be dried and then calcinedat a temperature ranging from about 250° C. to about 450° C., preferably400° C., under air for a time sufficient to thoroughly dry.

Compounds of formula I, II, III, and V of the present invention areuseful as catalysts in the oxidation of C4 hydrocarbons. The presentinvention provides a process for the oxidation of C4 hydrocarbons tomaleic anhydride, comprising: contacting the C4 hydrocarbon with asource of oxygen in the presence of a catalytic amount of a catalystcomprising a molybdenum compound of formula I, II, III or V as definedabove. The C4 hydrocarbon is selected from the group consisting of:n-butane, 1-butene, 2-butene and butadiene, and isomers thereof.

In some instances the catalyst may he useful as a lattice oxygencatalyst in the oxidation of C4 hydrocarbons with the ability toselectively oxidize the C4 hydrocarbon in the absence of gas phaseoxygen and thus can be the only source of oxygen.

The catalyst comprising the molybdenum compound of formula I, II, III orV can be used alone, supported on a catalyst support or impregnated in acarrier material. Typical support carrier materials are well known tothose skilled in the art as are methods of preparing supported orimpregnated catalysts. Typical materials comprise silica, titania,zirconia, alumina, thoria, silicon carbide and carbon. The catalystcomprising the molybdenum compound described herein can be used asisolated, or in cases where size and shape of the catalyst is dictatedby the requirements of the equipment employed in the subsequent use ofthe catalyst, the catalyst can be processed or fabricated into varioussize and shape particles before use by grounding, pelletizing,briquetting, tabulating, or shaping in other ways as required.

A first group of compounds, listed in Table 1 as Examples 1-5, are offormula I: V_(q)MoA_(y)O_(z), where q varies from 0.1 to 1.0, y variesfrom 0.1 to 10, A is at least one cation selected from the groupconsisting of cations of Cr, Sb, Co, Ce and Pb, and z is calculated asabove. The performance of these molybdenum compounds as catalysts in theoxidation of n-butane is shown in Table 1.

A second group of compounds, listed in Table 2 as Examples 6-9, are offormula II: NiMo_(x)B_(y)O_(z)′, where x varies from 0.1 to 10, y variesfrom 0.1 to 10, B is at least one cation selected from the groupconsisting of cations of Sb, Al and W and z′ is calculated as above. Theperformance of these molybdenum compounds as catalysts in the oxidationof n-butane is shown in Table 2.

A third group of compounds, listed in Table 3 as Examples 10-21, are offormula III: VNi_(w)Mo_(x)C_(y)′O_(z)″, where w varies from 0.1 to 10, xvaries from 0.1 to 10, y′ varies from 0 to 10, C is at least one cationselected from the group consisting of cations of Fe, Zn, Al, Sb, Bi, W,Li, Ba, Nb and Sn and z″ is calculated as above. The performance ofthese molybdenum compounds as catalysts in the oxidation of n-butane isshown in Table 3.

Another group of compounds, listed in Table 5 as Examples 27-35, are offormula V: VNi_(w)Co_(r)Mo_(x)E_(y)O_(z)″″, where w varies from 0.1 to10. r varies from 0.1 to 10, x varies from 0.1 to 10, y varies from 0.1to 10, E is at least one cation selected from the group consisting ofcations of Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb and z″″ iscalculated as above. The performance of these molybdenum compounds ascatalysts in the oxidation of n-butane is shown in Table 5.

The present invention further provides a process for the oxidation ofn-butane to maleic anhydride comprising contacting n-butane with asource of oxygen in the presence of a catalytic amount of a catalystcomprising a molybdenum compound of formula IV, as defined above, in abulk state. In some instances the catalysts comprising a molybdenumcompound of formula IV of the present invention are used as catalysts inthe bulk state, i.e., not on a support, but as pure compounds. Thecatalyst comprising the molybdenum compound of formula IV may be theonly source of oxygen. The catalytic oxidation can be carried out in afixed or fluidized bed reactor.

A group of compounds, listed in Table 4 as Examples 22-26, are offormula IV: CoNi_(w)Mo_(x)D_(y)O_(z)′″, where w varies from 0.1 to 10, xvaries from 0.1 to 10, y varies from 0.1 to 10, D is at least one cationselected from the group consisting of cations of Ba, Mn, Al, Sb, Sn andW, and z′″ is calculated as above. The performance of these molybdenumcompounds as catalysts in the oxidation of n-butane is shown in Table 4.

The present invention also provides a process for the oxidation ofn-butane to maleic anhydride, comprising: contacting n-butane with asource of oxygen in the presence of a catalytic amount of a catalystcomprising a molybdenum compound of formula VI or VII in a crystalline,active phase

V₉Mo₆O₄₀  VI

V₂MoO₈  VII

to yield maleic anhydride. Prepared as herein described, the molybdenumcompound of formula VI or VII is formed with little MoO₃ by-product. Theperformance of this molybdenum compound in a crystalline, active phaseas a catalyst in oxidation of n-butane is shown in Example 36 of Table6.

Comparative Examples 37-41, not of this invention, and the performanceof these materials as catalysts in the oxidation of n-butane is listedin Table 7.

Prior to use in the microreactor, the catalysts described herein aretypically formed into a convenient catalyst shape by pelletizing thecatalyst at about 30,000 psi (2.07×10⁶ kPa) or less, to form small disksand crushing the pellet through sieves. For fixed bed reactorevaluations, typically a −40, +60 mesh is used (U.S. Sieve Series).Optionally, one could blend the resultant powder with 1-3% of a dielubricant and pellet binder, such as graphite or Sterotex®, ahydrogenated cottonseed oil, commercially available from Capital CityProducts Company, Columbus, Ohio, before tabletting. For fluidized bedreactor use, the preferred size range is 20 to 150 micrometers.

Glass and stainless steel are usually employed as the material ofconstruction for the microreactor. This is not critical as long asmaterials that contaminate the product with catalyst poisons are notemployed.

Although processes of the invention are embodied in the followinglaboratory scale examples, Applicant notes that the invention can bepracticed on an industrial scale by making the necessary engineering anddesign modifications which are customary in the art.

Catalytic oxidation using a catalyst comprising a molybdenum compound offormula I, II, III, IV, V, VI or VII can be carried out in a fixed orfluidized bed reactor or recirculating solids reactor. These catalystscan be utilized advantageously with regard to conversion and selectivityin the wide variety of conventional techniques and reactorconfigurations employed to conduct the vapor phase oxidation of C4hydrocarbons to maleic anhydride. For example, the conversion can beconducted in a fixed-bed reactor, whereby the catalyst particles aremaintained in a fixed position and are contacted with C4 hydrocarbon anda source of oxygen, typically molecular oxygen, both in appropriateamounts, optionally in the presence of one or more inert diluent gases,at a temperature varying between 200° C. and about 450° C., preferablybetween about 300° C. and about 350° C. The greatest advantages of usingthe catalyst of this invention are realized when the conversion of C4hydrocarbon to maleic anhydride is carried out in a recirculating solidsreactor, such as that described in U.S. Pat. No. 4,668,802. This patentdiscloses an improved process for the selective vapor phase oxidation ofn-butane to maleic anhydride over a vanadium/phosphorus/oxygen (VPO)catalyst, whereby the amount of oxygen in the feed gas to the VPOcatalyst is limited to less than the stoichiometric amount required forthe total amount of n-butane converted in the process. The reducedcatalyst resulting from the oxidation is separated from the gaseousproduct stream and is reoxidized, optionally in a separate reactionzone, before being contacted with n-butane.

The catalysts of the present invention demonstrate good results inactivity, conversion and selectivity. Tables 1-6 below show conversionand selectivity after 1 sec and after 3 sec for various catalysts of thepresent invention and compare these results with those of othercatalysts in the art (Table 7).

EXAMPLES

The reagents for the following examples are commercially available asfollows: NH₄VO₃, Cr₂O₃, (CH₃CO₂)₇Cr₃(OH)₂, Ce(SO₄)₂, Fe(NO₃)₃-9H₂O,NbCl₅, Co(NO₃)₂-6H₂O, (CH₃CO₂)₂Mn-4H₂O, V₂O₅ and La(NO₃)₃-5H₂O fromAldrich, Milwaukee, Wis.; NH₄VO₃, MoO₃, Ni(OOCCH₃)₂-4H₂O, NiCl₂-6H₂O,H₂WO4, LiNO₃ (anhydrous), SnCl₂, (NH₄)₁₀W₁₂O₄₁-5H₂O, Co(NO₃)₂-6H₂O, andSnCl₂ from Alfa, Ward Hill, Mass.; (NH₄)₆Mo₇O₂₄-4H₂O), Ni(NO₃)-6H₂O,Al(NO₃)₃-9H₂O, Bi(NO₃)₃-5H₂O, Ni(NO₃)₂-6H₂O, Co(NO₃)₂-6H₂O,Al(NO₃)₃-9H₂O, Ca(NO₃)₂-4H₂O, and Ni(NO₃)₂, from Baker, Phillipsburg,N.J.; Pb(NO₃)₂, NiCl₂-6H₂O, Pb(NO₃)₂, and H₃PO₄ from EM Sciences,Gibbstown, N.J.; (NH₄)₆Mo₇O₂₄-4H₂O) from Mallinchkrodt, Erie, Pa.;NH₄VO₃, Sb(OOCCH₃)₃, Co(OOCCH₃)₂, Zr(SO₄)₂-4H₂O and Ga(NO₃)₃ from J&M,Ward Hill, Mass.; colloidal (Al₂O₃) from Nyacol, Ashland, Mass.;Zn(NO₃)₂-6H₂O from Fisher, Fairlane, N.J.; and Ba(NO₃)₂ and EuCl₂ fromAESAR, Ward Hill, Mass.

General Procedure for Freeze Drying

The component salts (indicated in the tables) were added to theindicated amount of water. In cases where NH₄VO₃ was used, the salt wasdissolved in water prior to adding, the other components by bringing thesolvent to a boil. The additional salts were then added to form thesolution or finely mixed colloid/slurry. The resultantsolutions/colloids were rapidly frozen in glass dishes (3″ diameter)using liquid nitrogen. The frozen material was then transferred to aVirtis Freeze Drier (Baltirnore, Md.) equipped with a Unitop unit. Inorder to prevent melting of the frozen solid, the Unitop chamber shelveswere maintained between −40 to −20° C. with a vacuum of 2-10 millitorr.After at least 24 hours (usually 2-4 days), the dried sample wascalcined (heated) in air to 400° C. for 5 hours to produce the finalcatalyst product. Prior to microreactor evaluations, the material waspelletized at 20,000 psi and crumbled and screened on −40, +60 meshscreens.

General procedure for Alcohol Reflux

Specific Preparation of V₂MoO₈

Vanadium pentoxide, V₂O₅, 90.94 g 0.500 mol, and molybdic oxide, MoO₃,71.97 g, 0.500 mol were combined in an round bottomed flask equippedwith an agitator with 1034 ml of isobutyl alcohol and 95 ml of benzyl.The resulting suspension was heated to reflux under a nitrogenatmosphere for 16 hours. The resulting green suspension was filtered andthe isolated product dried and then calcined at 400° C. under air for 5hours.

General Procedure for Gel Method

Specific preparation of NiMo_(2.3)AlO_(z)′

35 ml of water was added to the colloidal alumina (20% by weight). Thesolid oxide and nickel acetate was added. The mixture was stirred untilgelation occurred. The gel was dried then calcined at 400° C. under airfor 5 hours.

Micro-reactor Evaluation of Butane Oxidation Catalysts

The catalysts were pelletized at 1.38×10⁶ kPa into disks andsubsequently crushed and sieved through (−40, +60) mesh screens.Approximately 0.9 cc of catalyst were used for each evaluation.

The catalyst testing facility consisted of six micro-reactors which wereconnected to a common feed source and a common analytical gaschromatograph (GC). Each of the micro-reactors consisted of a 5.0 cm by0.64 cm stainless steel tube which was immersed in an individualsandbath to maintain isothermal conditions. The feed composition andindividual reactor flow rates were metered by commercially availablemass flow controllers (Tylan Model FC-260, available from Tylan Corp.Torrance. Calif.). All exit gas lines were heated to 200° C. andconnected to a multiport Valco valve for the on-line analysis ofproducts using a commercially available GC (Hewlitt-Packard 5890 SeriesII. Hewlitt-Packard, Palo Alto, Calif.). A computer program controlledthe Valco valve to select a reactor or feed stream to fill the 0.5 mlsample loop for injection in the GC. The GC was used to analyze forbutane, maleic anhydride, acetic acid, acrylic acid, other C₁ to C₄hydrocarbons, oxygen, carbon monoxide, carbon dioxide, nitrogen andwater.

The standard testing protocol for butane oxidation catalysts wasdeveloped to measure maleic anhydride selectivities and yields underhydrocarbon-lean conditions (2% n-butane, 20% oxygen) over a range ofbutane conversions. Temperature was varied from 350° to 380° to 400° andback to 350° C., with three contact times (nominally 3, 1, and 0.5 s)evaluated at each temperature. The temperature was returned to 350° C.to provide information about the equilibration of the catalyst. Theconversion and selectivity of two representative evaluations (at 380°C.) are reported in the tables below.

TABLE 1 380° C., 2.0% Butane/Air 1 sec 3 sec Composition Gram MoleMethod of Conversion Selectivity Conversion SelectivityV_(q)MoA_(y)O_(z) Example Salt Used Weight Solvent Synthesis % % % %V₁Mo₁Cr₁O_(z) 1 NH₄VO₃, 50% 116.98 250 ml H₂O freeze-dried 41 6 75 2V₂O₅ 50% 181.90 Cr₂O₃ 151.99 (CH₃CO₂)₇Cr₃(OH)₂ 602.32 (NH₄)₆Mo₇O₂₄-4H₂O1235.90 MoO₃ 143.94 V₁Mo₁Sb₁O_(z) 2 NH₄VO₃ 116.98 250 ml H₂Ofreeze-dried 75 7 99 2 (NH₄)₆Mo₇O₂₄-4H₂O 1235.90 Sb(OOCCH₃)₃ 298.88V₁Mo₁Co₁O_(z) 3 NH₄VO₃ 116.98 250 ml H₂O freeze-dried 70 3 99 0(NH₄)₆Mo₇O₂₄-4H₂O 1235.90 Co(OOCCH₃)₂ 177.023 V₁Mo₁Ce₁O_(z) 4 NH₄VO₃116.965 250 ml H₂O freeze-dried 18 9 45 4 (NH₄)₆Mo₇O₂₄-4H₂O 1235.9Ce(SO₄)₂ 332.24 V₁Mo₁Pb₁O_(z) 5 NH₄VO₃ 116.965 250 ml H₂O freeze-dried15 8 33 4 (NH₄)₆Mo₇O₂₄-4H₂O 1235.9 Pb(NO₃)₂ 331.2

TABLE 2 380° C., 2.0% Butane/Air Gram 1 sec 3 sec Composition MoleMethod of Conversion Selectivity Conversion SelectivityNiMo_(x)B_(y)O_(z′) Example Salt Used Weight Solvent Synthesis % % % %Ni₁Mo_(2.3)Sb₁O_(z′) 6 Sb(OOCCH₃)₃ 298.88 59 cc of freeze-dried 10 21 2612 (NH₄)₆Mo₇O₂₄-4H₂O 1235.9 30% HCl Ni(OOCCH₃)₂-4H₂O 248.82Ni₁Mo_(2.3)Al₁O_(z′) 7 Ni(OOCCH₃)₂-4H₂O 248.8212 35 ml H₂O gel 21  6 46<1 (NH₄)₆Mo₇O₂₄-4H₂O 1235.9 colloidal (Al₂O₃) 20% by 101.9613 wt.Ni₁Mo_(1.3)W₁O_(z′) 8 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 50 ml H₂O freeze-dried10 13 24  2 NiCl₂-6H₂O 237.71 70 ml NH₄OH H₂WO₄ 249.86 Ni₁Mo₁W_(1.3)_(O) _(z′) 9 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 40 ml H₂O freeze-dried 10 11 35 0 NiCl₂-6H₂O 237.71 90 ml NH₄OH H₂WO₄ 249.86 25 ml H₂O

TABLE 3 380° C., 2.0% Butane/Air Gram 1 sec 3 sec Composition Exam- MoleMethod of Conversion Selectivity Conversion SelectivityVNi_(w)Mo_(x)C_(y′)O_(z′) ple Salt Used Weight Solvent Synthesis % % % %V₁Mo_(2.3)Ni₁O_(z″) 10 NH₄VO₃ 116.98 100 cc H₂O freeze-dried 40 21 71 15(NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂O NiCl₂-6H₂O 237.71 20 cc HClV₁Mo_(2.3)Ni₁Fe₁O_(z″) 11 NH₄VO₃ 116.98 100 cc H₂O freeze-dried 28 7 60<1 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂O Ni(NO₃)-6H₂O 290.81 20 cc HNO₃Fe(NO₃)₃-9H₂O 404 V₁Mo_(2.3)Ni₁Zn₁O_(z″) 12 NH₄VO₃ 116.98 100 cc H₂Ofreeze-dried 53 6 83 <1 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂ONi(NO₃)-6H₂O 290.81 20 cc HNO₃ Zn(NO₃)₂-6H₂O 297.47V₁Mo_(2.3)Ni₁Al₁O_(z″) 13 NH₄VO₃ 116.98 100 cc H₂O freeze-dried 45 5 790 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂O Ni(NO₃)-6H₂O 290.81 20 cc HNO₃Al(NO₃)₃-9H₂O 375.13 V₁Mo_(2.3)Ni₁Sb₁O_(z″) 14 NH₄VO₃ 116.98 100 cc H₂Ofreeze-dried 39 10 69 5 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂ONi(NO₃)-6H₂O 290.81 15 cc HNO₃ Sb(OOCCH₃)₃ 298.88 50 cc HClV₁Mo_(2.3)Ni₁Bi₁O_(z″) 15 NH₄VO₃ 116.98 100 cc H₂O freeze-dried 20 15 507 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂O Ni(NO₃)-6H₂O 290.81 20 cc HNO₃Bi(NO₃)₃-5H₂O 485.07 30 cc HNO₃ V₁Mo_(2.3)Ni₁W₁O_(z″) 16 NH₄VO₃ 116.98100 cc H₂O freeze-dried 30 10 71 2 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 cc H₂ONi(NO₃)-6H₂O 290.81 20 cc HNO₃ H₂WO₄ 249.86 V₁Mo_(2.3)Ni₁Li₁O_(z″) 17NH₄VO₃ 116.98 100 ml H₂O freeze-dried 11 17 20 11 (NH₄)₆Mo₇O₂₄-4H₂O1235.86 NiCl₂-6H₂O 237.71 15 ml HCl LiNO₃ (anhydrous) 68.9459V₁Mo_(2.3)Ni₁Ba₁O_(z″) 18 NH₄VO₃ 116.98 100 ml H₂O freeze-dried 35 10 662 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 ml H₂O Ni(NO₃)-6H₂O 290.81 20 ml HNO₃Ba(NO₃)₂ 261.3398 V₁Mo_(2.3)Ni₁Nb₁Fe₁O_(z″) 19 NH₄VO₃ 116.98 100 cc H₂Ofreeze-dried 30 3 60 <1 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 50 cc H₂O NiCl₂-6H₂O237.71 20 cc HCl NbCl₅ 270.71 70 cc HCl Fe(NO₃)₃-9H₂O 404V₁Mo_(2.3)Ni₁Nb₁Sn₁O_(z″) 20 NH₄VO₃ 116.98 100 ml H₂O freeze-dried 40 1268 3 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 70 ml H₂O NiCl₂-6H₂O 237.71 20 ml HClNbCl₅ 270.17 20 ml HCl SnCl₂ 189.61 50 ml H₂O V₁Mo_(2.3)Ni₁W₁Sn₁O_(z″)21 (NH₄)₁₀W₁₂O₄₁₋ 3132.64 140 ml freeze-dried 25 10 47 3 5H₂O 1235.86NH₄OH (NH₄)₅Mo₇O₂₄-4H₂O 116.98 NH₄VO₃ 290.81 50 ml H₂O Ni(NO₃)₂-5H₂O189.61 SnCl₂ 5 ml HCl

TABLE 4 380° C., 2.0% Butane/Air 1 sec 3 sec Composition Gram MoleMethod of Conversion Selectivity Conversion SelectivityCoNi_(w)Mo_(x)D_(y)O_(z″) Example Salt Used Weight Solvent Synthesis % %% % Co_(0.5)Ni_(0.5)Mo₃ 22 Co(NO₃)₂-6H₂O 291.03 20 ml H₂O freeze-dried12.5 32 29 27 Sn_(0.5) _(O) _(z′′′) SnCl₂ 189.61 (NH₄)₆Mo₇O₂₄-4H₂O1235.86 50 ml H₂O NiCl₂-6H₂O 237.71 20 ml HNO₃ Mo₃Co_(0.5)Ni_(0.5) 23Co(NO₃)₂-H₂O 291.03 20 ml H₂O freeze-dried 1.3 4 2.3 11 Mn₁O_(z′′′)(CH₃CO₂)₂Mn-4H₂O 245.09 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 30 ml H₂O NiCl₂-6H₂O237.71 20 ml H₂O Mo₃Co_(0.5)Ni_(0.5) 24 Co(NO₃)₂-6H₂O 291.03 20 ml H₂Ofreeze-dried 0.8 16 2.1 18 Ba₁O_(z′′′) Ba(NO₃)₂ 261.34 (NH₄)₆Mo₇O₂₄-4H₂O1235.86 80 ml H₂O NiCl₂-6H₂O 237.71 20 ml H₂O Mo₃Co_(0.5)Ni_(0.5) 25Co(NO₃)₂-6H₂O 291.03 20 ml H₂O freeze-dried 3.9 15 10.5 8 Al₁O_(z′′′)Al(NO₃)₃-9H₂O 375.13 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 150 ml H₂O NiCl₂-6H₂O237.71 20 ml H₂O Mo₃Co_(0.5)Ni_(0.5) 26 Co(NO₃)₂-6H₂O 291.03 40 ml H₂Ofreeze-dried 4.2 27 14.2 15 W₁O_(z′′′) (NH₄)₁₀W₁₂O₄₁-5H₂O 3132.64(NH₄)₆Mo₇O₂₄-4H₂O 1235.86 50 ml H₂O NiCl₂-6H₂O 237.71 10 ml H₂O

TABLE 5 380° C., 2.0% Butane/Air Gram 1 sec 3 sec Composition Exam- MoleMethod of Conversion Selectivity Conversion SelectivityVNi_(w)Co_(r)Mo_(x)E_(y)O_(z′′′) ple Salt Used Weight Solvent Synthesis% % % % V₁Mo_(2.3)Ni_(0.5)Co_(0.5) 27 NH₄VO₃ 116.98 50 ml H₂Ofreeze-dried 15 13 32 7 Fe₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 20 ml H₂OCo(OOCCH₃)₂ 177.02 20 ml HCl Ni(NO₃)₂-6H₂O 290.81 Fe(NO₃)₃-9H₂O 404 20ml H₂O V₁Mo_(2.3)Ni_(0.5)Co_(0.5) 28 NH₄VO₃ 116.98 50 ml H₂Ofreeze-dried 14 10 34 4 Ca₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86Co(OOCCH₃)₂ 177.02 20 ml HCl Ni(NO₃)₂-6H₂O 290.81 5 ml HCl Ca(NO₃)₂-4H₂O236.15 V₁Mo_(2.3)Co_(0.5)Ni_(0.5) 29 NH₄VO₃ 116.98 50 ml H₂Ofreeze-dried 12.5 2.5 29.2 1 Mn₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 20ml H₂O Co(OOCCH₃)₂ 177.02 20 ml HCl Ni(NO₃)₂-6H₂O 290.81(CH₃CO₂)₂Mn-4H₂O 245.09 10 ml H₂O V₁Mo_(2.3)Co_(0.5)Ni_(0.5) 30 NH₄VO₃116.98 50 ml H₂O freeze-dried 21 17 47 10 Sr₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O1235.86 20 ml HCl Co(OOCCH₃)₂ 177.02 10 ml H₂O Ni(NO₃)₂-6H₂O 290.81Sr(NO₃)₂ 211.63 V₁Mo_(2.3)Co_(0.5)Ni_(0.5) 31 NH₄VO₃ 116.98 50 ml H₂Ofreeze-dried 24 7.5 54 2 Eu₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86Co(OOCCH₃)₂ 177.02 20 ml HCl Ni(NO₃)₂-6H₂O 2908.1 EuCl₂ 222.87 10 ml H₂OV₁Mo_(2.3)Co_(0.5)Ni_(0.5) 32 NH₄VO₃ 116.98 50 ml H₂O freeze-dried 17 1036 5 La₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 Co(OOCCH₃)₂ 177.02 20 ml HClNi(NO₃)₂-6H₂O 290.81 La(NO₃)₃-5H₂O 415.01 10 ml H₂OV₁Mo_(2.3)Co_(0.5)Ni_(0.5) 33 NH₄VO₃ 116.98 50 ml H₂O freeze-dried 2017.5 46 12 Zr₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 Co(OOCCH₃)₂ 177.02 20ml HCl Ni(NO₃)₂-6H₂O 290.81 Zr(SO₄)₂-4H₂O 355.32 40 ml H₂OV₁Mo_(2.3)Co_(0.5)Ni_(0.5) 34 NH₄VO₃ 116.98 50 ml H₂O freeze-dried 1816.5 43 11 Ga₁O_(z′′′′) (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 Co(OOCCH₃)₂ 177.02 20ml HCl Ni(NO₃)₂-6H₂O 290.81 Ga(NO₃)₃ 255.74 V₁Mo_(2.3)Co_(0.5)Ni_(0.5)35 NH₄VO₃ 116.98 50 ml H₂O freeze-dried 22 20 47 14 Pb₁O_(z′′′′)(NH₄)₆Mo₇O₂₄-4H₂O 1235.86 (with dry ice Co(OOCCH₃)₂ 177.02 20 ml HCl andacetone) Ni(NO₃)₂-6H₂O 290.81 Pb(NO₃)₂ 331.2 100 ml HCl 86 ml NH₄OH

TABLE 6 380° C., 2.0% Butane/Air Gram 1 sec 3 sec Exam- Mole Method ofConversion Selectivity Conversion Selectivity Composition ple Salt UsedWeight Solvent Synthesis % % % % V₂Mo₁O_(x) 36 V₂O₅ 90.94 g 181.88 1034ml isobutyl alcohol Alcohol reflux 60 10 90 0 MoO₃ 71.97 g 143.94 95 mlbenzyl alcohol

TABLE 7 380° C., 2.0% Butane/Air 1 sec 3 sec Comp. Gram Mole Method ofConversion Selectivity Conversion Selectivity Composition Example SaltUsed Weight Solvent Synthesis % % % % MoO₃ 37 (NH₄)₆Mo₇O₂₄-4H₂O 1235.9freeze-dried 11 <1 VPO 38 NH₄VO₃ 116.965 freeze-dried 8 20 H₃PO₄ 97.97Ni₁W_(2.3)O_(t) 39 H₂WO₄ 249.86 50 ml H₂O freeze-dried 2.5 0 9 0NiCl₂-6H₂O 237.71 180 ml NH₄OH Ni₁Mo_(2.3)P₁O_(t) 40 Ni(NO₃)₂ 290.8 50ml H₂O freeze-dried 6 12 (NH₄)₆Mo₇O₂₄-4H₂O 1235.86 100 ml H₂O H₃PO₄ 98V₂O₅ 41 freeze-dried 80 <1

What is claimed is:
 1. A catalyst, comprising a molybdenum compound offormula I, II, III, IV or V: V_(q)MoA_(y)O_(z)  INiMo_(x)B_(y)O_(z)′  II VNi_(w)Mo_(x)C_(y)′O_(z)″  IIICoNi_(w)Mo_(x)D_(y)O_(z)′″  IV VNi_(w)Co_(r)Mo_(x)E_(y)O_(z)″″  Vwherein: q is a number from 0.1 to 10; r is a number from 0.1 to 10; wis a number from 0.1 to 10; x is a number from 0.1 to 10; y is a numberfrom 0.1 to 10; y′ is a number from 0 to 10, A is at least one cationselected from the group consisting of cations of: Cr, Ce and Pb; B is atleast one cation selected from the group consisting of cations of: Aland W, C is at least one cation selected from the group consisting ofcations of: Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn; D is at least onecation selected from the group consisting of cations of: Ba, Mn, Al, Sb,Sn, and W; E is at least one cation selected from the group consistingof cations of: Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb; and z, z′, z″,z′″, and z″″ are determined using the amounts and oxidation states ofall cations present in each formula according to the followingequations: z=((q times oxidation state of V)+(1 times oxidation state ofMo)+(y times oxidation state of A)) divided by 2 (oxidation state ofoxygen); z′=((1 times oxidation state of Ni)+(x times oxidation state ofMo)+(y times oxidation state of B)) divided by 2 (oxidation state ofoxygen); z″=((1 times oxidation state of V)+(w times the oxidation stateof Ni)+(x times oxidation state of Mo)+(y′ times oxidation state of C))divided by 2 (oxidation state of oxygen); z′″=((1 times oxidation stateof Co)+(w times the oxidation state of Ni)+(x times oxidation state ofMo)+(y′ times oxidation state of D)) divided by 2 (oxidation state ofoxygen); and z″″=((1 times oxidation state of V)+(w times the oxidationstate of Ni)+(r times the oxidation state of Co)+(x times oxidationstate of Mo)+(y′ times oxidation state of E)) divided by 2 (oxidationstate of oxygen).
 2. The catalyst of claim 1 wherein the molybdenumcompound is of formula I.
 3. The catalyst of claim 1 wherein themolybdenum compound is of formula II.
 4. The catalyst of claim 1 whereinthe molybdenum compound is of formula III.
 5. The catalyst of claim 1wherein the molybdenum compound is of formula IV.
 6. The catalyst ofclaim 1 wherein the molybdenum compound is of formula V.